At startup, the Oracle ASM instance attempts to mount the following disk groups:
Disk groups specified in the ASM_DISKGROUPS initialization parameter
Disk group used by Cluster Synchronization Services (CSS) for voting files
Disk groups used by Oracle Clusterware for Oracle Cluster Registry (OCR)
Disk group used by the Oracle ASM instance to store the ASM server parameter file (SPFILE)
If no disk groups are found in the previous list, then the Oracle ASM instance does not mount any disk groups at startup. After the Oracle ASM instance has started, you can mount disk groups with the ALTER DISKGROUP...MOUNT command. For more information, see "Mounting and Dismounting Disk Groups".